1. Field of the Invention
The present invention relates to graphic printing in a multi-color printer.
2. Description of the Prior art
It has been a common practice to display a calculation result by a graph in order to facilitate visual recognition the status. Some of office computers, personal computers and desk-top calculators with printers have graph printing functions. Many office computers and personal computers use multi-color CRT displays to display the graphs in a readily recognisable way. Multi-color printers for color-printing the multi-color graphs have been developed.
Usually, red, green and blue are the basic colors used in the CRT display, and yellow, magenta, cyan and white are additionally used to display the graph. However, when a yellow pattern which is clearly visible on the CRT display is printed on white paper, it is very unclear and hard to distinguish. When seven-color printing is made by the printer, cyan, magenta and yellow are used as basic colors and those colors are mixed to print red, green, blue and black patterns. (Sometimes, black ink is separately provided.)
Because the yellow print is hard to distinguish, it may be modified to a color tone which is easier to distinguish. However, the colors which are synthesized by yellow and other colors are affected. Therefore, the color tone cannot be changed significantly and the print remains hard to distinguish. Particularly in the graph printing, a boundary with other color printing is hard to distinguish, or it is hard to determine whether the area is printed or blank.